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| author | Petr Mladek <pmladek@suse.com> | 2021-04-29 22:54:33 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-05-19 10:13:00 +0200 |
| commit | 5b66867966bc04652d85d58b8500a22b99aa5dad (patch) | |
| tree | a246b85a77a32ec788e653fbdb87ee9f2b6bc94f /kernel/watchdog.c | |
| parent | a68c246065b6042bfdb9177527fcf0e8f93dff3d (diff) | |
| download | linux-stable-5b66867966bc04652d85d58b8500a22b99aa5dad.tar.gz linux-stable-5b66867966bc04652d85d58b8500a22b99aa5dad.tar.bz2 linux-stable-5b66867966bc04652d85d58b8500a22b99aa5dad.zip | |
watchdog: fix barriers when printing backtraces from all CPUs
[ Upstream commit 9f113bf760ca90d709f8f89a733d10abb1f04a83 ]
Any parallel softlockup reports are skipped when one CPU is already
printing backtraces from all CPUs.
The exclusive rights are synchronized using one bit in
soft_lockup_nmi_warn. There is also one memory barrier that does not make
much sense.
Use two barriers on the right location to prevent mixing two reports.
[pmladek@suse.com: use bit lock operations to prevent multiple soft-lockup reports]
Link: https://lkml.kernel.org/r/YFSVsLGVWMXTvlbk@alley
Link: https://lkml.kernel.org/r/20210311122130.6788-6-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel/watchdog.c')
| -rw-r--r-- | kernel/watchdog.c | 17 |
1 files changed, 6 insertions, 11 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 122e272ad7f2..01bf977090dc 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -393,11 +393,12 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) if (kvm_check_and_clear_guest_paused()) return HRTIMER_RESTART; + /* + * Prevent multiple soft-lockup reports if one cpu is already + * engaged in dumping all cpu back traces. + */ if (softlockup_all_cpu_backtrace) { - /* Prevent multiple soft-lockup reports if one cpu is already - * engaged in dumping cpu back traces - */ - if (test_and_set_bit(0, &soft_lockup_nmi_warn)) + if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn)) return HRTIMER_RESTART; } @@ -415,14 +416,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) dump_stack(); if (softlockup_all_cpu_backtrace) { - /* Avoid generating two back traces for current - * given that one is already made above - */ trigger_allbutself_cpu_backtrace(); - - clear_bit(0, &soft_lockup_nmi_warn); - /* Barrier to sync with other cpus */ - smp_mb__after_atomic(); + clear_bit_unlock(0, &soft_lockup_nmi_warn); } add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); |